In recent years, easy handling of digital image data has been realized by improved performance of the CPU and development of image processing technique. Especially the cellular phones and PDA (Personal Digital Assistance) provided with a display unit capable of image display have become available on the market and the drastic improvement in radio communication speed can be expected in the very near future. Accordingly, frequent transfer of image data is considered to be made among cellular phones and PDA.
At present, a subject is converted into an image data by a digital still camera or the like, and such an image data is then transferred via a personal computer or the like via the Internet. This method however requires both a digital still camera and a personal computer to be purchased in order to transfer image data. On the other hand, attempts have been made to mount such an image device as a CCD (Charge Coupled Device) type image sensor on the cellular phone. Such an attempt will eliminate the need of purchasing a digital still camera and personal computer, and will provide easy means of sending an image to a counterpart device through a cellular phone which can be easily carried.
At present, however, the weight of a cellular phone will be increased if the cellular phone is equipped with the function of a large-sized digital still camera which is much larger than the cellular phone, with the result that the phone cannot be easily carried. In addition to this problem, the manufacturing cost will be increased that much.
Even if an image pick-up optical system and an image pick-up device as major components of the digital still camera, a photo-electric conversion unit of the image pick-up device must be properly set at the focusing position of the image pick-up optical system. This raises the problem of how to make this adjustment. For example, when the image pick-up device and image pick-up optical system are to be installed on one and the same base board, it can be said to be difficult to install the photo-electric conversion unit of the image pick-up device at the focusing position of the image pick-up optical system with high precision due to such factors as variations in the thickness of adherent used for mounting on the base board or variations in the dimensions of component parts. Accordingly, an advanced level of high precision installation technique is essential or a separate mechanism is necessary to adjust the focusing position, in order to improve the precision of mounting the photo-electric conversion unit of the image pick-up device at the focusing position of the image pick-up optical system. This will raise the manufacturing cost. The following cities an example to describe the problems involved in the prior art.
FIG. 6 is a cross sectional view representing an example of the image pick-up apparatus according to the prior art. An image pick-up device 110 is laid out on the base board PC made of glass epoxy, and is connected to the image processing IC circuit 111 provided on the back surface of the base board PC via multiple wires W leading from the stop surface of a terminal (not illustrated).
A first enclosure 101 is provided so as to cover the image pick-up device 110, and a second enclosure 102 is mounted thereon. They are locked together on the base board by means of bolts 103. An infrared ray cutoff filter is arranged between the first enclosure 101 and second enclosure 102.
The top of the second enclosure 102 is cylindrical, and the lens body tube 105 enclosing a lens 106 is mounted in such a way that the position of this body tube can be adjusted in the direction of optical axis with respect to the second enclosure 102 by meshing a male screw 105a with a female screw 102a formed inside the second enclosure 102. A lens aperture 105b is formed on the top of the lens body tube 105.
Such an image pick-up apparatus according to the prior art is a comparatively large-sized apparatus comprising multiple component parts. In addition to the above-mentioned high cost problems, this configuration will require a lot of time in assembling these parts, and the relative position between the image pick-up device 110 and lens 106 must be adjusted by rotating the lens body tube 105 at the time of assembling.
To solve these problems, an attempt has been made to provide the lens with a supporting part extended close to the focus position. This part is brought into direct contact with the image pick-up device, thereby configuring an image pick-up apparatus according to this attempt. This attempt allows an easy layout of the photo-electric conversion unit of the image pick-up device at the focusing position of the lens, with the result that a substantial amount of time and labor can be saved to assemble an image pick-up apparatus.
However, this method raises the problem of what profile the lens supporting part should have. For example, three or four legs are extended from the lens toward the image pick-up device. These legs, however, has a problem of being easily deformed by external force. If legs are deformed, a deviation is caused between the photo-electric conversion unit of the image pick-up device and lens focusing point, and this may deteriorate the image quality.
Another problem is how to manufacture an image pick-up lens where the periphery of a lens is extended in the direction of optical axis. If plastic is used as a material, a mass production of image pick-up lens of stable quality can be achieved by injection molding using a mold. If injection molding is used, however, burrs are likely to be formed on the split portion of the mold. When the gate is cut off, burrs are also likely to occur. Depending on the position of these burrs, the assembling precision may be deteriorated, with the result that function of the image pick-up device may not be fully performed.
A further problem is how to adjust the positional relationship between the surface formed by the tip of supporting part and lens surface in order to ensure precise layout of the photo-electric conversion unit of the image pick-up device.